1. Field of the Invention
This invention relates to a photosensitive resin composition, and more particularly to a photosensitive resin composition useful as materials for forming protective insulating films for semiconductor devices, orientation films for liquid-crystal display devices, insulating films for multi-layer printed-circuit boards.
2. Description of the Prior Art
What have been hitherto proposed as heat-resistant photosensitive materials are exemplified by a material comprising polyamic acid and dichromate [Japanese Patent Publication (kokoku) No. 49-17374 corresponding to U.S. Pat. No. 3,623,870], a material comprising a polyamic acid into the carboxylic acid of which a photosensitive group has been introduced through an ester linkage [Japanese Pre-examination Patent Publication (kokai) Nos. 49-115541 corresponding to U.S. Pat. No. 3,957,512 and 55-45746], a material comprising polyamic acid and an amine compound having a photosensitive group [Japanese Pre-examination Patent Publication (kokai) 54-145794 corresponding to U.S. Pat. No. 4,243,743], a material comprising a polyamic acid into the carboxylic acid of which a photosensitive group has been introduced through a silyl ester linkage [Japanese Pre-examination Patent Publication (kokai) No. 62-275129].
Since, however, these materials are polyimide resin precursors (polyamic acids), the precursors are exposed to light to form a pattern and thereafter the pattern must be heated usually at a temperature higher than 300.degree. C. Accordingly, substrates on which these materials are used are limited to those capable of withstanding such a high temperature.
Meanwhile, a photosensitive resin comprising polyimide as a base skeleton is proposed which is exemplified by a negative photosensitive resin into the polyimide skeleton of which a photopolymerizable functional group has been introduced (Japanese Pre-examination Patent Publication (kokai) Nos. 60-72925 and 61-59334), or a positive photosensitive resin composition comprised of a polyimide, which has a phenolic hydroxyl group, and a diazonaphthoquinone [Japanese Pre-examination Patent Publication (kokai) No. 3-209478 corresponding to U.S. Pat. No. 5,288,5881] is proposed.
However, films formed on substrates by using the photosensitive polyimide resin have no sufficient adhesion to the substrates. Also, corrosive ions may remain in the photosensitive polyimide resin films or in films having been cured, to cause, e.g., corrosion of metals. Hence, this greatly comes into question when the photosensitive polyimide resin is used in electronic materials.